The correct spelling of the phrase "wast at head of" is actually "waste at the head of". The phonetic transcription for this phrase is /weɪst æt ðə hɛd əv/. The word "waste" means an area of land that is uncultivated or not used for its intended purpose. The phrase "at the head of" means at the top or beginning of something. So, together the phrase "waste at the head of" refers to an uncultivated area at the beginning of something, such as a river or valley.